As a chemical reaction occurs, the thermometer in the container records an increase in temperature. what is true of the reaction?

the reaction is endothermic because heat was taken in by the reaction.

the reaction is exothermic because heat was released by the reaction.

the reaction is endothermic because heat was released by the reaction.

the reaction is exothermic because heat was taken in by the reaction.

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.